Transient global amnesia: current perspectives

Chronic hippocampal subfield damage in transient global amnesia revealed by 7T MRI: All is not reversible?

Transient global amnesia (TGA) is a neurological condition characterized by temporary memory loss and classically associated with a reversible unilateral punctate focus of restricted diffusion in the cornu ammonis 1 (CA1) region of the hippocampus. Historically, the lesions were considered to be transient in nature with no long-term imaging abnormality. However, more recent studies have challenged the concept that there are no long-term neurological sequelae. In line with this evidence, we explore the role of ultra-high-resolution imaging using 7 Tesla MRI to evaluate for long-term imaging abnormalities in a 63-year-old woman with a typical clinical course and acute TGA imaging findings. The 7 Tesla MRI revealed a residual lesion on susceptibility-weighted imaging (SWI) with evidence of gliosis and volume loss at the site of the acute lesion in CA1 eight months after the acute episode. This case challenges the traditional mantra of TGA as a fully reversible condition with no long-term imaging findings, suggesting the need for further research using ultra-high-field MRI to determine TGA's potential long-term imaging sequelae and any association with neurocognitive sequelae.

Altered cerebellar volumes and intrinsic cerebellar networks in patients with transient global amnesia

This study aimed to investigate the differences in cerebellar volumes and intrinsic cerebellar networks between patients with transient global amnesia (TGA) and healthy controls. We retrospectively enrolled patients with TGA and age- and sex-matched healthy controls. We used three-dimensional T1-weighted imaging at the time of TGA diagnosis to obtain cerebellar volumes, and the intrinsic cerebellar network was calculated by applying graph theory based on cerebellar volumes. The nodes were defined as individual cerebellar volumes, and edges as partial correlations, controlling for the effects of age and sex. The cerebellar volumes and intrinsic cerebellar networks were compared between the two groups. We enrolled 44 patients with TGA and 47 healthy controls. The volume of the left cerebellar white matter in patients with TGA was significantly lower than that in healthy controls (1.0328 vs. 1.0753%, p = 0.0094). In addition, there were significant differences in intrinsic cerebellar networks between the two groups. The small-worldness index in patients with TGA was higher than that in the healthy controls (0.951 vs. 0.880, p = 0.038). In the correlation analysis, the volumes of the right cerebellar cortex and lobules VIIIB were significantly correlated with age in patients with TGA (r = -0.323, p = 0.033; r = -0.313, p = 0.038, respectively). Patients with TGA exhibit alterations in cerebellar volumes and intrinsic cerebellar networks compared with healthy controls. These findings may contribute to a better understanding of the pathophysiology of the TGA.

Changes in heart rate variability over time from symptom onset of transient global amnesia

Transient global amnesia (TGA) often involves precipitating events associated with changes in autonomic nervous system (ANS), and heart rate variability (HRV) reflects the ANS state. This study aimed to investigate HRV changes after TGA. A retrospective analysis of HRV included patients diagnosed with TGA between January 2015 and May 2020. The time and frequency domains of HRV were compared among three groups: early (< 1 week after TGA, n = 19), late (1-4 weeks after TGA, n = 38), and healthy control (HC, n = 19). The Pearson's correlation between time and time-domain HRV was also examined. The standard deviation of NN intervals (SDNN) (early, 47.2; late, 35.5; HC, 41.5; p = 0.033) and root mean square of successive RR interval differences (RMSSD) (early, 38.5; late, 21.3; HC, 31.0; p = 0.006) differed significantly among the three groups. Post-hoc analysis showed statistically significant differences only in the early and late groups in both SDNN (p = 0.032) and RMSSD (p = 0.006) values. However, the frequency domain with total power, low-frequency and high-frequency powers, and low-frequency/high-frequency ratio did not differ. SDNN (Pearson correlation coefficient =- 0.396, p = 0.002) and RMSSD (Pearson correlation coefficient =- 0.406, p = 0.002) were negatively correlated with time after TGA. Changes in HRV occurred over time after the onset of TGA, with the pattern showing an increase in the first week and then a decrease within 4 weeks.

A case report on concomitant reversible cerebral vasoconstriction syndrome and transient global amnesia

Reversible Cerebral Vasoconstriction Syndrome clinically presents as severe headaches with or without neurological deficits accompanied by multilocal caliber variation of the cerebral arteries on imaging studies. Transient Global Amnesia is a benign neurological condition that implies sudden temporary antero- and retrograde amnesia. The exact pathophysiological mechanisms involved in transient global amnesia and reversible cerebral vasoconstriction syndrome remain unclear but suggest similar pathways as both can be triggered by factors that activate the sympathetic nervous system. We herein discuss a potential relationship of the two conditions in a 65-year-old woman that initially presented herself to the emergency department with temporary memory impairment, indicating Transient Global Amnesia. Four days later, the patient revealed a thunderclap headache accompanied by a subarachnoid hemorrhage with transient segmental narrowing of the arteries of the anterior circulation on neuroimaging. In this case report we hypothesize that Reversible Cerebral Vasoconstriction Syndrome might be a potential cause for the clinical symptoms and imaging patterns with Transient Global Amnesia as a possible prodromal stage of Reversible Cerebral Vasoconstriction Syndrome.

Prolonged Transient Global Amnesia: Part of the Clinical Spectrum or a Separate Disease Entity?

Background

Transient global amnesia (TGA) is the prototypical neurologic disease for acute-onset reversible amnesia. It is currently defined by resolution of symptoms within 24-hours. In this case report we describe an atypical case of prolonged TGA, emphasizing our current lack of knowledge surrounding this disease entity and its pathophysiology.

Results

A 66-year old female presented acutely with profound anterograde amnesia and variable retrograde amnesia with no inciting event. A thorough workup to exclude alternative causes of amnesia (including computed tomography angiogram and electroencephalogram) was normal. Her magnetic resonance imaging was consistent with TGA, with punctate diffusion restriction changes bilaterally in the hippocampi. She was also mildly hypoxemic with no discernible cause. She was ultimately diagnosed with TGA although her diagnosis remains controversial as her symptoms persisted for 72-hours.

Conclusion

Our patients clinical and imaging features (apart from her protracted time-course and hypoxemia) were in keeping with a diagnosis of TGA. The association of hypoxemia, COVID-19, obstructive sleep apnea, and the development of TGA remains to be elucidated. Although the underlying pathophysiology for TGA is unknown several mechanisms have been postulated including cortical spreading depression and reversible hypoxic-ischemic injury. The time course for symptom resolution, could be an important clue in discerning the pathophysiology of TGA on an individual basis. Importantly, a clinician should not be deterred by amnestic symptoms lasting >24-hours, if the patients clinical/radiologic presentation is consistent with TGA.

Case of transient global amnesia-like syndrome after recreational cold-water swimming

We document a case of a transient global amnesia (TGA)-like syndrome following open water swimming. This case was atypical for TGA, in that symptoms were prolonged and ischaemic infarct was considered within the differential. MRI did not demonstrate any changes associated with acute ischaemia although did show a mild degree of small vessel change. With amnesia taking greater than 24 hours to resolve, we have labelled this case to be a TGA-like syndrome, provoked by the commonly reported TGA precipitant of cold water immersion. The possibility of a tiny, strategic infarct causing these symptoms was considered and antiplatelet therapy commenced.

Mitochondrial dynamics, elimination and biogenesis during post-ischemic recovery in ischemia-resistant and ischemia-vulnerable gerbil hippocampal regions

Transient ischemic attacks (TIA) result from a temporary blockage in blood circulation in the brain. As TIAs cause disabilities and often precede full-scale strokes, the effects of TIA are investigated to develop neuroprotective therapies. We analyzed changes in mitochondrial network dynamics, mitophagy and biogenesis in sections of gerbil hippocampus characterized by a different neuronal survival rate after 5-minute ischemia-reperfusion (I/R) insult. Our research revealed a significantly greater mtDNA/nDNA ratio in CA2-3, DG hippocampal regions (5.8 ± 1.4 vs 3.6 ± 0.8 in CA1) that corresponded to a neuronal resistance to I/R. During reperfusion, an increase of pro-fission (phospho-Ser616-Drp1/Drp1) and pro-fusion proteins (1.6 ± 0.5 and 1.4 ± 0.3 for Mfn2 and Opa1, respectively) was observed in CA2-3, DG. Selective autophagy markers, PINK1 and SQSTM1/p62, were elevated 24-96 h after I/R and accompanied by significant elevation of transcription factors proteins PGC-1α and Nrf1 (1.2 ± 0.4, 1.78 ± 0.6, respectively) and increased respiratory chain proteins (e.g., 1.5 ± 0.3 for complex IV at I/R 96 h). Contrastingly, decreased enzymatic activity of citrate synthase, reduced Hsp60 protein level and electron transport chain subunits (0.88 ± 0.03, 0.74 ± 0.1 and 0.71 ± 0.1 for complex IV at I/R 96 h, respectively) were observed in I/R-vulnerable CA1. The phospho-Ser616-Drp1/Drp1 was increased while Mfn2 and total Opa1 reduced to 0.88 ± 0.1 and 0.77 ± 0.17, respectively. General autophagy, measured as LC3-II/I ratio, was activated 3 h after reperfusion reaching 2.37 ± 0.9 of control. This study demonstrated that enhanced mitochondrial fusion, followed by late and selective mitophagy and mitochondrial biogenesis might together contribute to reduced susceptibility to TIA.

A neurostructural biomarker of dissociative amnesia: a hippocampal study in dissociative identity disorder

BACKGROUND

Little is known about the neural correlates of dissociative amnesia, a transdiagnostic symptom mostly present in the dissociative disorders and core characteristic of dissociative identity disorder (DID). Given the vital role of the hippocampus in memory, a prime candidate for investigation is whether total and/or subfield hippocampal volume can serve as biological markers of dissociative amnesia.

METHODS

A total of 75 women, 32 with DID and 43 matched healthy controls (HC), underwent structural magnetic resonance imaging (MRI). Using Freesurfer (version 6.0), volumes were extracted for bilateral global hippocampus, cornu ammonis (CA) 1-4, the granule cell molecular layer of the dentate gyrus (GC-ML-DG), fimbria, hippocampal-amygdaloid transition area (HATA), parasubiculum, presubiculum and subiculum. Analyses of covariance showed volumetric differences between DID and HC. Partial correlations exhibited relationships between the three factors of the dissociative experience scale scores (dissociative amnesia, absorption, depersonalisation/derealisation) and traumatisation measures with hippocampal global and subfield volumes.

RESULTS

Hippocampal volumes were found to be smaller in DID as compared with HC in bilateral global hippocampus and bilateral CA1, right CA4, right GC-ML-DG, and left presubiculum. Dissociative amnesia was the only dissociative symptom that correlated uniquely and significantly with reduced bilateral hippocampal CA1 subfield volumes. Regarding traumatisation, only emotional neglect correlated negatively with bilateral global hippocampus, bilateral CA1, CA4 and GC-ML-DG, and right CA3.

CONCLUSION

We propose decreased CA1 volume as a biomarker for dissociative amnesia. We also propose that traumatisation, specifically emotional neglect, is interlinked with dissociative amnesia in having a detrimental effect on hippocampal volume.

Transient global amnesia after COVID-19: A systematic scoping review of case reports

Background: Transient global amnesia (TGA) is a sudden-onset transient memory impairment along with intact neurologic examinations. Even though it is a benign neurologic condition with many differential diagnoses, the incidence rate of TGA is reported to have increased since the onset of the pandemic. Therefore, this systematic scoping review aims to investigate TGA in that context. Methods: MEDLINE, Scopus, and Google Scholar databases were systematically searched for relevant articles with a string of specified keywords. Results: The primary search yielded 90 studies. After all the necessary screening rounds were carried out, we were left with six included studies. One study was also identified through a search in other relatively relevant databases. Finally, seven case reports were accepted including three TGA patients with positive and one with negative test for coronavirus disease-2019 (COVID-19), respectively. COVID-19 status was unclear in the others. Conclusion: The reported COVID-19 positive cases had presentations similar to those with TGA before the pandemic. Therefore, we think that TGA might occur concomitantly with the COVID-19 infection or due to the psychological impact of the pandemic. In the confirmed cases of TGA and COVID-19, the abnormal findings may be due to COVID-19 infection. However, the reports were not as complete as desired. Therefore, providing the readers with more detailed reports in future cases is recommended.

Forgetting the Unforgettable: Transient Global Amnesia Part II: A Clinical Road Map

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of a temporary memory disorder with profound anterograde amnesia and a variable impairment of the past memory. Usually, the attacks are preceded by a precipitating event, last up to 24 h and are not associated with other neurological deficits. Diagnosis can be challenging because the identification of TGA requires the exclusion of some acute amnestic syndromes that occur in emergency situations and share structural or functional alterations of memory circuits. Magnetic Resonance Imaging (MRI) studies performed 24–96 h after symptom onset can help to confirm the diagnosis by identifying lesions in the CA1 field of the hippocampal cornu ammonis, but their practical utility in changing the management of patients is a matter of discussion. In this review, we aim to provide a practical approach to early recognition of this condition in daily practice, highlighting both the lights and the shadows of the diagnostic criteria. For this purpose, we summarize current knowledge about the clinical presentation, diagnostic pathways, differential diagnosis, and the expected long-term outcome of TGA.

Cognitive deficits and memory impairments after COVID-19 (Covishield) vaccination

Vaccination is an essential public health strategy to control the 2019 Coronavirus (COVID-19) pandemic. While the benefits of the COVID-19 vaccines far outweigh the risks, side effects continue to be reported in the literature. We report a 65-year-old man who developed cognitive deficits and memory impairments following his first dose of Oxford AstraZeneca vaccine (Covishield). The onset of acute cognitive deficits and memory impairments could be another complication to COVID-19 vaccination that physicians and neurologists need to be warned to. Monitoring the safety of COVID-19 vaccines and describing side effects associated with them is essential to improve safety profiles and enhance public trust.

Forgetting the Unforgettable: Transient Global Amnesia Part I: Pathophysiology and Etiology

Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of a temporary memory disorder with a profound anterograde amnesia and a variable impairment of the past memory. Since the first description, dating back over 60 years, several cases have beenreported in the literature. Nevertheless, TGA remains one of the most mysterious diseases in clinical neurology. The debate regarding the etiology of this disease has focused mainly on three different mechanisms: vascular (due to venous flow changes or focal arterial ischemia), epileptic, and migraine related. However, to date there is no scientific proof of any of these mechanisms. Furthermore, the demonstration by diffusion-weighted MRI of lesions in the CA1 field of the hippocampus cornu ammonis led us to hypothesize that the selective vulnerability of CA1 neurons to metabolic stress could play a role in the pathophysiology of TGA. In this review, we summarize current knowledge on the anatomy, vascularization and function of the hippocampus. Furthermore, we discuss the emerging theories on the etiology and the pathophysiological cascade leading to an impairment of hippocampal function during the attacks.

Neuroimaging and Electroencephalographic Correlation in Patients with Transient Global Amnesia: Clinical Case Series

Objective. To determine if there is any correlation between the electroencephalographic and neuroimaging findings in patients with Transient Global Amnesia (TGA). Methods: We retrospectively reviewed files of the First Department of Neurology of AHEPA University Hospital, including patients with a clinical diagnosis of TGA. Only patients who had the characteristic high signal in the temporal lobes in the DWI MRI and those who underwent electroencephalographic recording (EEG) were selected. Results: Out of 28 patients, 8 were selected. We found that 6 out of 8 patients (75%) who had imaging findings in DWI, in at least one medial temporal lobe, also had had intermittent slow theta waves on the electroencephalographic recording. Of these 6 patients, 3 (50%) had bilateral EEG findings, 2 patients (33,3%) only had findings on the left hemisphere and 1 (17%) had on the right hemisphere. 3 out of 6 patients (50%) had electroencephalographic dominance on the left, while 2 out of the 6 (33%) had on the right. In 2 patients with imaging findings in DWI no anomalies were demonstrated on EEG. In 3 out of 8 patients, both MRI and EEG findings correlated on the same side, while 1 patient had opposite findings, depending on which hemisphere the EEG anomalies dominated. Conclusions: There is no absolute matching between the DWI MRI and EEG findings in patients with the clinical diagnosis of TGA. However, there is some degree of correlation, when we focus on the focal dominance of the EEG anomalies, although not statistically significant.

Acute-onset amnesia: transient global amnesia and other causes

Acute-onset amnesia is a dramatic neurological presentation that can cause considerable concern to both patient and clinician. The patient typically presents with an inability not only to retain new memories but also to access previously acquired memories, suggesting disturbance of hippocampal function. Transient global amnesia (TGA) is the most common cause of acute-onset amnesia, and is characterised by a profound anterograde and retrograde amnesia that typically lasts for up to 24 hours. Although TGA has a strikingly stereotypical presentation, it can be challenging to distinguish from other causes of acute-onset amnesia, including posterior circulation strokes, transient epileptic amnesia, psychogenic amnesia, post-traumatic amnesia, and toxic/drug-related amnesia. Here, we describe the general approach to the patient with acute amnesia; summarise the clinical and neuropsychological differences between the potential causes; and, provide practical recommendations to aid diagnosis and management of acute amnesia. Regardless of cause and the dramatic presentation, non-ischaemic acute-onset amnesia generally has a favourable prognosis.

A Case of Transient Global Amnesia: A Rare Diagnosis

Transient global amnesia (TGA) is a syndrome characterized by a loss of anterograde memory with a less prominent loss in retrograde episodic memory that resolves within 24 hours or less. In this report, we present a rare case of a 62-year-old male who presented to the emergency department with sudden onset confusion and memory loss. Prior to this, the patient had no significant medical or psychiatric history. Magnetic resonance imaging (MRI) and computerized tomography (CT) showed a normal presentation, and a neurology consultation ruled out any organic brain abnormalities. After ruling out all other potential causes, diagnosis of transient global amnesia was made. We present this case highlighting the importance of ruling out other acutely morbid conditions when addressing TGA, guidance on timing of imaging, as well as offering insight on other etiologies of this condition.

Transient Global Amnesia - Risk Factors and Putative Background

Objectives

Transient global amnesia (TGA) is a temporary short-term reversible memory loss. Etiology of TGA remains unclear with various hypotheses. We analyzed clinical characteristics, neuroimaging, and electrophysiological findings as well as comorbidities and seasonal variation in TGA patients with regard to possible background of the syndrome.

Materials and Methods

A total of 56 patients (42 women and 14 men) with TGA hospitalized from 2008 to 2016 in the Department of Neurology, Wrocław Medical University.

Results

A total of 52 patients (92.9%) underwent their first-ever episode of TGA. The potential triggers or events before episode could be recognized in 22 patients (39.3%). 35.7% patients had TGA in summer and 26.8% in winter months. In 92.9% patients chronic diseases were found, included: Hypertension (60.7%), dyslipidemia (48.2%), autoimmune thyroiditis (17.9%), and ischemic heart disease (14.3%). One patient (1,8%) suffered from migraine. Doppler ultrasonography of carotid arteries revealed abnormalities in 29 patients (51.8%). Electroencephalography abnormalities were observed in 10 (17.6%) of patients.

Conclusion

Our findings suggest a putative cerebrovascular background of transient global amnesia. No evidence has been provided for the association between TGA and epilepsy or migraine. Among comorbidities, autoimmune thyroiditis deserves further investigation with regard to its potential links with TGA.

Conventional cardiovascular risk factors in Transient Global Amnesia: Systematic review and proposition of a novel hypothesis

Transient Global Amnesia (TGA) is an enigmatic amnestic syndrome. We conducted a systematic review to investigate the relationship between the conventional cardiovascular risk factors and TGA. MEDLINE, CENTRAL, EMBASE and PsycINFO were comprehensively searched and 23 controlled observational studies were retrieved. The prevalence of hypertension, diabetes mellitus, dyslipidemia and smoking was lower among patients with TGA compared to Transient Ischemic Attack. Regarding the comparison of TGA with healthy individuals, there was strong evidence suggesting a protective effect of diabetes mellitus on TGA and weaker evidence for a protective effect of smoking. Hypertension was associated with TGA only in more severe stages, while dyslipidemia was not related. In view of these findings, a novel pathophysiological hypothesis is proposed, in which the functional interactions of Angiotensin-II type-1 and N-methyl-D-aspartate receptors are of pivotal importance. The whole body of clinical evidence (nature of precipitating events, associations with migraine, gender-based association patterns) was integrated.

Transient global amnesia after radiofrequency catheter ablation of supraventricular tachycardia: a case report

Transient global amnesia (TGA) is a neurological disorder characterized by sudden onset of anterograde amnesia with or without retrograde amnesia, lasting less than 24 hours, without other clinical neurological dysfunction. TGA with short duration and benign prognosis is usually neglected in clinical practice. Transient total amnesia after radiofrequency ablation is rare and its etiology is unknown. We report a case of 27-year-old man who experienced TGA after radiofrequency catheter ablation of supraventricular tachycardia. The patient had no other cognitive and motor impairment except for memory impairment. The symptom lasted for about six hours and relieved without recurrence. Nervous system examination showed that 12 pairs of cranial nerves were normal, the muscle strength and muscle tone of the limbs were normal, physiological reflexes existed, and no pathological reflexes were elicited. Tests were performed immediately and normally including blood routine examination, liver and kidney function, electrolyte, blood glucose, thyroid function, blood coagulation function, D-dimer, myocardial injury markers, blood gas analysis and other hematological. There is no abnormality in electrocardiogram (ECG), chest X-ray, cervical vascular ultrasound, and cardiac color Doppler ultrasound examination. Head magnetic resonance examination magnetic resonance imaging (MRI) showed dots in right frontal lobe and bilateral ventricles in T2-weighted images. There was no cerebral infarction and cerebral hemorrhage. The patient received low flow oxygen inhalation and aspirin 300mg orally. The outcome of patient with TGA is benign. There are still many unsolved mysteries worthy of long-term follow-up.

Transient global amnesia: Signal alteration in 2D/3D T2-FLAIR sequences

PURPOSE

Transient global amnesia (TGA) is one of the most enigmatic syndromes in clinical neurology. The detection rate of TGA lesions in 2D/3D FLAIR sequences has not been evaluated.

METHODS

A total of 201 patients (44 men and 157 women; mean age, 60.34 ± 9.23 years; range, 22-91 years) diagnosed with TGA, who underwent diffusion-weighted imaging (DWI; b = 1000 s/mm², b = 2000 s/mm², 4 mm) and/or 2D/3D-FLAIR sequences (4 mm, 0.9 mm; respectively) using 3-T MRI within 28 days after onset of TGA symptoms, were included in this single-center, retrospective, cross-sectional study. Hippocampal lesions were visually assessed in all sequences and detection rates were analyzed according to imaging timing (1 day, 2-4 days, 5-7 days, 8-11 days, and 12-28 days) and kinds of sequences.

RESULTS

The detection rates were highest 2-4 days after symptom onset in all sequences, and that was higher in order of b = 2000 (75.28% [67/89]), b = 1000 (63.92% [62/97]), 3D-FLAIR (59.38% [19/32]), and 2D-FLAIR (15.15% [15/99]). On FLAIR sequences, detectability was lower 5-7 days after onset than that 2-4 days after onset (2D-FLAIR, 15.15% [15/99] vs. 5.56% [1/18]; 3D-FLAIR, 59.38% [19/32] vs. 0.00% [0/1]).

CONCLUSION

FLAIR signal changes occur in approximately 60% of TGA patients 2-4 days after symptom onset, and decrease after 5 days. It is postulated that the pathophysiology of TGA might differ from common ischemic changes.

Can you have a migraine aura without knowing it?

PURPOSE OF REVIEW

This review covers several aspects our understanding of episodic manifestations and unusual symptoms that may be associated with migraine aura.

RECENT FINDINGS

The episodic manifestation of migraine aura is typically visual in nature, although five other types are currently recognized: sensory, speech and/or language, motor, brainstem, and retinal. Other transitory perceptions or experiences such as emotional, olfactory, or auditory have been reported as possible migraine auras. As underlined by the much higher reported prevalence of aura manifestation in individuals with professional knowledge of its possible manifestations, it appears that a number of migraine auras may remain unnoticed, unreported, or misdiagnosed.

SUMMARY

Aura manifestations may be more common, complex, symptom-rich and variable than previously thought. Clinicians should proactively ask questions beyond those addressing visual symptoms when examining individuals with a potential diagnosis of migraine with aura.

The long-term prognosis of Transient Global Amnesia: a systematic review

Transient Global Amnesia (TGA) constitutes an enigmatic amnestic condition. In view of the admittedly limited knowledge regarding the nature of TGA, we decided to systematically review existing evidence for the generally regarded benign course of the disease. MEDLINE, EMBASE, CENTRAL and PsycINFO were searched for relevant articles. Observational (case-control, cross-sectional and cohort) controlled studies were retrieved. TGA diagnosis was made according to the diagnostic criteria of Caplan, validated by Hodges and Warlow. The TGA group was compared with either healthy controls (HC) or/and individuals with transient ischaemic attacks (TIA). The long-term risks of dementia, epilepsy, psychological-emotional disturbances, as well as long-term vascular and (vascular or nonvascular) mortality risks, were evaluated. Quality assessment was based on the Newcastle-Ottawa Scale. Literature search provided 12 eligible articles. Retrospective, prospective or mixed cohort designs were implemented in every study. Five articles registered a high quality, five registered a moderate quality, while two articles were assessed as part of the grey literature (conference abstract, abstract in English-article in Spanish). Overall, retrieved evidence was suggestive of similar vascular and mortality risks in TGA patients and HC, while TIA individuals exhibited elevated risks. Moreover, psychological disturbances were comparable between TGA and healthy individuals. On the other hand, studies for dementia and epilepsy obtained contradictory results, indicating both a similar and an increased risk in the TGA group compared to the HC group. Therefore, additional high-quality studies are warranted for the acquisition of more determining conclusions regarding the long-term risk of dementia and epilepsy in TGA.

Power Spectral Differences between Transient Epileptic and Global Amnesia: An eLORETA Quantitative EEG Study

Transient epileptic amnesia (TEA) is a rare epileptic condition, often confused with transient global amnesia (TGA). In a real-life scenario, differential diagnosis between these two conditions can be hard. In this study we use power spectral analysis empowered by exact Low Resolution Brain Electromagnetic Tomography (eLORETA) to evidence the differences between TEA and TGA. Fifteen patients affected by TEA (64.2 ± 5.2 y.o.; 11 female/4 male; 10 left and 5 right temporal epileptic focus) and 15 patients affected by TGA (65.8 ± 7.2 y.o.; 11 females/4 males) were retrospectively identified in our clinical records. All patients recorded EEGs after symptoms offset. EEGs were analyzed with eLORETA to evidence power spectral contrast between the two conditions. We used an inverse problem solution to localize the source of spectral differences. We found a significant increase in beta band power over the affected hemisphere of TEA patients. Significant results corresponded to the uncus and para-hippocampal gyrus, respectively Brodmann’s Areas: 36, 35, 28, 34. We present original evidence of an increase in beta power in the affected hemisphere (AH) of TEA as compared to TGA. These differences involve key areas of the memory network located in the mesial temporal lobe. Spectral asymmetries could be used in the future to recognize cases of amnesia with a high risk of epilepsy.

Cortical Spreading Depolarization in Chronic Subdural Hematoma: Bridging the Gap

Cortical spreading depolarization (CSD) is recognized as a cause of transient neurological symptoms (TNS) in various clinical entities. Although scientific literature has been flourishing in the field of CSD, it remains an underrecognized pathophysiology in clinical practice. The literature evoking CSD in relation to subdural hematoma (SDH) is particularly scarce. Patients with SDH frequently suffer from TNS, most being attributed to seizures despite an atypical semiology, evolution, and therapeutic response. Recent literature has suggested that a significant proportion of those patients' TNS represent the clinical manifestations of underlying CSD. Recently, the term Non-Epileptical Stereoytpical Intermittent Symptoms (NESIS) has been proposed to describe a subgroup of patients presenting with TNS in the context of SDH. Indirect evidence and recent research suggest that the pathophysiology of NESIS could represent the clinical manifestation of CSD. This review should provide a concise yet thorough review of the current state of literature behind the pathophysiology of CSD with a particular focus on recent research and knowledge regarding the presence of CSD in the context of subdural hematoma. Although many questions remain in the evolution of knowledge in this field would likely have significant diagnostic, therapeutic, and prognostic implications.

Transient Global Amnesia in a 60-year-old female with Post-traumatic Stress Disorder

This is a case report involving a 60-year-old female who developed transient global amnesia (TGA) after an emotional psychotherapy session in the framework of post-traumatic stress disorder (PTSD). She presented to the local emergency room, three days after her psychotherapist appointment, with complaints of memory impairment. She and her husband were worried about acute stroke since it was a sudden memory loss. The patient discussed with her psychotherapist a physical assault that occurred five years ago. Three days after that discussion, the patient developed the memory loss acutely. PTSD is associated with dissociative and retrograde amnesia. This case report demonstrates that PTSD can present with anterograde amnesia in the form of TGA.

Loss of Function of Phosphodiesterase 11A4 Shows that Recent and Remote Long-Term Memories Can Be Uncoupled

Systems consolidation is a process by which memories initially require the hippocampus for recent long-term memory (LTM) but then become increasingly independent of the hippocampus and more dependent on the cortex for remote LTM. Here, we study the role of phosphodiesterase 11A4 (PDE11A4) in systems consolidation. PDE11A4, which degrades cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), is preferentially expressed in neurons of CA1, the subiculum, and the adjacently connected amygdalohippocampal region. In male and female mice, deletion of PDE11A enhances remote LTM for social odor recognition and social transmission of food preference (STFP) despite eliminating or silencing recent LTM for those same social events. Measurement of a surrogate marker of neuronal activation (i.e., Arc mRNA) suggests the recent LTM deficits observed in Pde11 knockout mice correspond with decreased activation of ventral CA1 relative to wild-type littermates. In contrast, the enhanced remote LTM observed in Pde11a knockout mice corresponds with increased activation and altered functional connectivity of anterior cingulate cortex, frontal association cortex, parasubiculum, and the superficial layer of medial entorhinal cortex. The apparent increased neural activation observed in prefrontal cortex of Pde11a knockout mice during remote LTM retrieval may be related to an upregulation of the N-methyl-D-aspartate receptor subunits NR1 and NR2A. Viral restoration of PDE11A4 to vCA1 alone is sufficient to rescue both the LTM phenotypes and upregulation of NR1 exhibited by Pde11a knockout mice. Together, our findings suggest remote LTM can be decoupled from recent LTM, which may have relevance for cognitive deficits associated with aging, temporal lobe epilepsy, or transient global amnesia.

Anterograde Amnesia as a Manifestation of Acute Type A Aortic Dissection

Objectives  Memory impairment has been only rarely reported in association with acute aortic dissection type A. We report a patient with pure anterograde amnesia and memory impairment of contents occurring after the event, accompanying acute aortic dissection type A. Case Report  A previously healthy 53-year-old Caucasian male was admitted because of sudden chest pain after having lifted a heavy object. Clinical examination and electrocardiogram showed no abnormalities. Since blood tests showed leukocytosis, anemia, and elevated D-dimer level, either pulmonary embolism or aortic dissection was suspected; therefore, computed tomography was suggested. The patient seemed disoriented to time, and neurologic investigation confirmed that the patient was disoriented to time; short time memory was severely impaired and concentration was reduced. An amnestic episode with anterograde amnesia was diagnosed. Computed tomography showed type A aortic dissection. A supracoronary replacement of the ascending aorta was performed. The patient was discharged on the 7th postoperative day. Three months postoperatively, the patient is clinically stable; however, amnesia for the interval between pain onset and cardiac surgery persists. Conclusions  Transient amnesia, usually considered a benign syndrome, may be more common than generally recognized in aortic dissection. The suspicion for aortic dissection or other cardiovascular emergencies is substantiated when amnesia is associated with sudden onset of chest pain, leukocytosis, and elevated D-dimer levels. Computed tomography of the aorta with contrast medium is the imaging method of choice to confirm or exclude the diagnosis.

Tissue Level Mechanical Properties and Extracellular Matrix Investigation of the Bovine Jugular Venous Valve Tissue

Jugular venous valve incompetence has no long-term remedy and symptoms of transient global amnesia and/or intracranial hypertension continue to discomfort patients. During this study, we interrogate the synergy of the collagen and elastin microstructure that compose the bi-layer extracellular matrix (ECM) of the jugular venous valve. In this study, we investigate the jugular venous valve and relate it to tissue-level mechanical properties, fibril orientation and fibril composition to improve fundamental knowledge of the jugular venous valves toward the development of bioprosthetic venous valve replacements. Steps include: (1) multi loading biaxial mechanical tests; (2) isolation of the elastin microstructure; (3) imaging of the elastin microstructure; and (4) imaging of the collagen microstructure, including an experimental analysis of crimp. Results from this study show that, during a 3:1 loading ratio (circumferential direction: 900 mN and radial direction: 300 mN), elastin may have the ability to contribute to the circumferential mechanical properties at low strains, for example, shifting the inflection point toward lower strains in comparison to other loading ratios. After isolating the elastin microstructure, light microscopy revealed that the overall elastin orients in the radial direction while forming a crosslinked mesh. Collagen fibers were found undulated, aligning in parallel with neighboring fibers and orienting in the circumferential direction with an interquartile range of -10.38° to 7.58° from the circumferential axis (n = 20). Collagen crimp wavelength and amplitude was found to be 38.46 ± 8.06 µm and 4.51 ± 1.65 µm, respectively (n = 87). Analyzing collagen crimp shows that crimp permits about 12% true strain circumferentially, while straightening of the overall fibers accounts for more. To the best of the authors' knowledge, this is the first study of the jugular venous valve linking the composition and orientation of the ECM to its mechanical properties and this study will aid in forming a structure-based constitutive model.